Sunday, December 27, 2015

In North America and Europe, camels generally keep a low profile except for December, when they show up as part of Christmas iconography: the Three Wise Men, Nativity scenes, etc. The general scarcity of camels in these landmasses makes them exotic. Camels and llamas today evoke specific areas: camels bring to mind deserts from north Africa into central Asia, and llamas are shorthand for the Andes. However, camelids (including camels, llamas, alpacas, and so forth) are actually a North American innovation, circa middle Eocene. Through no particular fault of their own, there are now no longer any native camel species in North America, although as recently as the late Pleistocene, about 126,000 to 11,700 years ago, camels were common. The two flagship models at this time were Camelops hesternus, which translates to the evocative "yesterday's camel", and Hemiauchenia macrocephalus, also known as the "North American llama". The exact taxonomy, of course, is somewhat more bushy when you get into it, but this isn't bad for broad strokes. The camel family filled a number of niches in North America over the Cenozoic, from what we would recognize as roles similar to modern camels and llamas, to giraffe analogues like Aeypcamelus, to plus-sized forms like Megacamelus and Titanotylopus, to analogues of deer and gazelle, such as Poebrotherium (also of note as the first fossil organism named from the White River Badlands; Prout's "Palaeotherium" doesn't count because he didn't actually name it). Here are a couple of examples from the now-vanished North American empire of camels:

Sunday, December 13, 2015

Fort Monroe at Old Point Comfort in southeastern Virginia, today the namesake attraction of Fort Monroe National Monument, has a long and distinguished history. It also hosts an odd little geologic story. If you're familiar with Chesapeake geology, you may guess the punchline, but don't spoil it for everyone else, okay?

Fort Monroe, during the early stages of the Civil War. Not pictured: somebody contemplating where to sink a well, never dreaming that by the time they stopped in 1869, the war would be long over, the current President would be assassinated, his replacement would be impeached, and the well would only turn up salt water. (image found at NPS monument site).

For understandable reasons, it is useful for a fort to have a secure water supply. Logically enough, the staff at Fort Monroe decided to address theirs by drilling an artesian well. Thus it was that in 1845, work began on a well. Drilling continued until July 1846, at which time a pipe broke at 189 ft (58 m). In terms of getting water, this effort was unsuccessful, but for those of us interested in geology and paleontology, the attempt was a rousing success. The pioneering American microscopist Jacob Whitman Bailey identified a number of fossils, particularly from a unit of fine-grained greenish gray sand 48 to 108 ft (15 to 33 m) down). Identifiable material included coal, foraminifera, stratigraphically useful bivalves and scaphopods, and echinoid spines (Fontaine 1882). The mollusks are typical of the Yorktown Formation, now known to be Pliocene.

By the time of the Civil War, the fort (which remained in Union hands throughout) was still reliant on a cistern. Another attempt to sink a well was begun in 1864, within the walls of the fort (Woolman 1899). This time they reached 907 ft (276 m) (Rogers 1882) before running out of money in September 1869 (Fontaine 1882). Again, a number of marine fossils were found in the sediments, this time also including abundant diatoms, shark teeth, and whale bones (Rogers 1882). Also, like the first well, there was a distinct lack of potable groundwater. The only significant water was struck at 599 ft (183 m), and it was reportedly very saline (Sanford 1913).

There is no sense in doing things halfway, so in 1902 a third attempt was made. This time, they didn't stop until they penetrated crystalline bedrock at 2,254 ft (687 m) (Darton 1902). In eastern Virginia, there aren't a lot of places to view long columns of strata, so this and the 1864 well have attracted a fair amount of interest, popping up from time to time in the literature (e.g. Richards 1945, 1947; Cederstrom 1945, 1957; Powars 2000). Interestingly, Darton (1902) thought there was quite a bit of Cretaceous coastal plain sediments below the fossil-bearing Cenozoic marine sediments, but Cederstrom (1945, 1957) thought it was Cenozoic all the way down. In the end, the well has been quite informative for geologists. In terms of water? The third and final attempt was just as fruitless as the others. When water was tested, it proved to be saline (Sanford 1913).

Now for the punchline: they never turned up potable groundwater for the simple reason that they couldn't. What they had no way of knowing at the time was that during the Eocene, approximately 35 million years ago, an object from space blasted into North America about where the tip of the Delmarva Peninsula is today. Fort Monroe happens to be within the area directly affected by the impact. The sediments down to bedrock were rearranged in the blink of an eye and the preexisting aquifers were completely disrupted. In the impact zone, no matter how far down you go, you turn up salty water (Powars and Bruce 1999; Powars 2000).

Sunday, December 6, 2015

Ankylosaurians, be they clubbed or club-less, labor in relative anonymity among dinosaurs, bundles of roughage trundling along, only briefly intersecting the limelight of flashier dinosaurs. A few get a bit more press, enough to put them in a respectable second tier of popularity (Ankylosaurus and Gastonia, particularly). Despite being the traditional namesake for the club-less ankylosaurs*, Nodosaurus is not one of them. Instead, it fills a role not unlike a venerable distant relative who occasionally shows up at family functions to hover on the sidelines. We know he or she is there and we show due deference, but there's no particularly warm connection of familiarity. The closest it's gotten to a star turn since it was named in 1889 was as a John Sibbick illustration in the "Normanpedia", where it is depicted as a sort of vaguely armadillo-like creature suspiciously eyeing the reader and bearing a precise gridwork of button-like armor pieces, without a hint of spikes or plates. Oddly, the skeletal restoration on the next page shows a distinctly different pattern of armor, featuring alternating bands of large scutes between the ribs and smaller pieces over the ribs, which unintentionally give it a sort of corduroy texture. As we shall see, there does indeed appear to a corduroy pattern over part of the animal, but there was also a lot more going on.

*This great tradition goes back all the way to the 1970s (Coombs 1978). Prior to this, ankylosaurs were just kind of there as one sort of mash. After this, ankylosaurs were still just kind of there, but now there were two flavors.

Saturday, November 28, 2015

You're probably pretty busy this weekend. How about something light, like some photos? These all come from a few site visits over October and November, taking advantage of the very pleasant autumn weather conditions in the Twin Cities metro.

This and the next photo come from the U.S. Route 10 roadcuts, in the Shakopee Formation (Prairie du Chien Group). All of the little stone rainbows are small domed stromatolites. At very close range, you can distinguish between layers that are "crystalline", so to speak, representing minerals deposited by the microbes, and layers of sand (a grain or two thick). There is a band populated by these small stromatolites about as thick as the area photographed here that extends for at least a few tens of meters. (I do not recommend casual visits along this busy road; the couple of times I've stopped have been Sunday mornings.)

Saturday, November 21, 2015

"Somebody's got to tell the tale/I guess it must be up to me" — B. Dylan

Among all the other oddities we encountered in the Glut (1982) series in the summer, there was one purported sauropod of particular obscurity, from "Kweichow" (Guizhou). I figured it was the specimen described in Young [Yang] (1948), but was somewhat discomfited to find that it had made itself scarce in the years since 1948. There weren't even any dinosaurs listed in "The Dinosauria" from Guizhou. Had it been re-evaluated as non-dinosaurian, or actually come from a different province? To my surprise, the journal was listed as "in storage" in the University of Minnesota library system, so I fired off an interlibrary loan request and in a few days was the proud owner of a shiny new pdf. Acting on the principle that every dinosaur deserves its day, I present the "Kweichow sauropod".

Sunday, November 8, 2015

My day job as a paleontological researcher for the National Park Service often involves writing paleontological resource inventory reports for inventory and monitoring networks. Each report consists of chapters on the paleontology of each park in a given network. For example, I am currently working on the Mojave Desert I&M Network. This network includes Death Valley National Park, Great Basin National Park, Joshua Tree National Park, Lake Mead National Recreation Area, Manzanar National Historic Site, Mojave National Preserve, and Parashant National Monument; we'll also throw in Tule Springs Fossil Beds National Monument, because it's geographically within the network, and if it had existed at the time the networks were created, it would certainly have have been included. In the past week, I just finished writing a draft for Mojave National Preserve. When I work on these reports, in essence I have to become passably conversant with the geology and paleontology of an area I probably know little to nothing about within a few weeks. Having done this kind of work since 2008, I have worked up a system that so far has worked pretty well for me.

Saturday, October 31, 2015

This is being posted on Halloween, which is fitting for a topic that lingers like a ghost in the literature. Even today, you can still find stray references to the fossils of Pipestone National Monument. "Occasional small trilobites - Lingula, Paradoxides" sounds promising, doesn't it? If you're reasonably familiar with the fossils of Minnesota, you may be wondering why you never heard of this before. There's a pretty good reason: these forgotten fossils are not trilobites or brachiopods, and odds are they are not fossils at all.

Sunday, October 25, 2015

The stats for Equatorial Minnesota have recently shown visitors looking for "Minnesota dinosaur", no doubt because of the recentannouncement of a ~90 million-year-old theropod claw from Hill Annex Mine State Park on the Iron Range. Minnesota, as you might know, is not noted for its dinosaur fossils. (I usually have to add the modifier "non-avian" or "classic" to "dinosaur", but I don't know of any bird fossils, either, unless you want to count refuse bones from archeological sites. Maybe the St. Peter Sandstone holds a buried Pleistocene-age cave in a filled river channel somewhere...) However, there are a handful of reports of Cretaceous dinosaurs from Minnesota.

Sunday, October 18, 2015

The last of the fossils to be covered to complete the Upper Ordovician Twin Cities set (barring some microfossils and real rarities) are a nebulous group of oft-times enigmatic organisms that either are algae, or have been classified as algae. "Algae" is a much more problematic a term than you might suspect. To put it simply, "algae" is more of a state of mind than a formal classification. At its broadest, "algae" covers basically anything that does photosynthesis and doesn't have the obvious distinct tissues of derived plants, like leaves and roots. This would include anything from diverse microbes to seaweeds. While this has some utility for back-of-the-envelope things, it is not the most useful term for serious classification. It should not be surprising that untold numbers of fossils have been been classified as algae, and that many of these "algae" belong to disparate groups, some of which still have unsettled classifications. About a half-dozen taxa from the Platteville, Decorah, and basal Cummingsville formations have fallen into the "algae" bin at one time or another. They include the following:

Saturday, October 10, 2015

National Fossil Day is this Wednesday, October 14th. The 16th birthday of Thescelosaurus would have been last Wednesday, October 7th. In honor of both, here is The Compact Thescelosaurus, a sortable spreadsheet of basic information on classic (non-avian) dinosaur species, minus names that have not been formally described. I began working on it shortly after I decided to end the website; I still wanted the information to be available, but I also wanted something that was lower-maintenance, and more flexible to edit. This is what I came up with. The other nice thing about it was that I updated a number of things, which I can now use to clean up my original files and perhaps make them available as pdfs, for people who miss the dry commentary and the nomina nuda. This wouldn't happen for several more months, though. Anyway, here's a short user guide to the spreadsheet below the jump, column by column. If someone wants to use the format for some other group, they are free to do so. Otherwise, have fun!

[A quick note, 2015-10-12: I've received a couple of inquiries about being added as editors. I appreciate the interest, but at this time, I'd prefer to keep this project under one person. Feel free to send corrections and other information, though! (I consider many aspects of taxonomy to be matters of judgement, so we many have to agree to disagree on those matters.)]

Saturday, October 3, 2015

A common yet easily overlooked type of fossil is the conodont (or "conodont element", should we choose to be picky and/or technical). They are easy to overlook because they are sub-millimeter-scale fossils, which makes them just barely visible to the naked eye if you look really hard. Most of the time, though, all you can do is to take bulk samples of rock and run them acids to liberate these tiny fossils; conodont fossils are made of calcium phosphate, so they will not be dissolved by some acids that do dissolve calcium carbonate, i.e. limestone. Having dissolved your limestone, you can then inspect the remainder under a microscope. Ideally, you will have some little pointy toothy bits, which are the conodont elements.

Saturday, September 19, 2015

Graptolites are one of the less-heralded members of the local Ordovician menagerie, probably because they don't seem to be all that common around here. Graptolites were colonial animals (and I use "were" and other past-tense terminology with implied quotation marks, because of the shocking twist yet to come). The colonies, called "rhabdosomes", are made up of branches called "stipes", which support cup-like structures called "theca" that housed the individual animals. (See also here for official terminology.) The overall effect is that stipes often resemble saw blades, with the "teeth" being the theca. Early graptolites were apparently attached to the seafloor and formed densely branching (dendritic) colonies (see for example several of the specimens here and here), whereas later forms were apparently planktonic and attached to floats of their own device or other floating things, such as seaweeds. The rapid taxonomic turnover of graptolites, coupled with the ease of distribution for planktonic forms, make them excellent index fossils. Planktonic distribution also has the neat side effect of getting graptolites into rock formations that otherwise lack much for fossils, usually because of low oxygen levels in the water column precluding a great deal of life while the formation was being deposited. While low oxygen would limit bottom dwellers, it wouldn't stop things from drifting through higher up the water column. Fossils of graptolites are found from the Cambrian into the Carboniferous. This may not be where the story ends, though: it has been known for a while that graptolites are most similar to pterobranchs, a living group of tube-dwelling often-colonial worm-like hemichordates. There is evidence that pterobranchs are, in fact, living graptolites (e.g. Mitchell et al. 2013; Discovery Magazine ran an article on this topic back in 1993). Should this be the case, it would appear that only the planktonic forms truly disappeared; seafloor forms persisted, albeit in much reduced circumstances (only a handful of pterobranch genera and species are known). All of the species reported from the Twin Cities appear to be of the planktonic persuasion.

As mentioned, graptolites are an uncommon component of the local fauna. They do pop up from time to time, though, and their thin dark saw blade fossils are quite distinctive if you get a large enough chunk. Reports of graptolites in the Twin Cities go back almost to the beginning of local geology, actually. Shumard (1852) reported graptolites from a bluff about a half-mile downstream from Fort Snelling, in what would now be considered the lower Platteville Formation. Winchell and Schuchert (1895) provided illustrations for three species, Climacograptus typicalis, Diplograptus pristis?, and Diplograptus putillus. All of their cited specimens came from outside the metro, and apparently from higher stratigraphically than virtually all metro rocks, with C. typicalis from what would now be the Cummingsville Formation and the other two from what would now be the Dubuque Formation, per the stratigraphic table in Winchell and Ulrich (1897). Stauffer (1930) found abundant black fragments of graptolites in a particularly calcareous layer low in the Decorah Shale in rocks recovered from a heating shaft dug for Northrop Auditorium. Stauffer and Thiel (1941) observed C. typicalis in what would now be the Mifflin Member at Lock and Dam 1, on the Ramsey County side. Their lists reported three following species in the Platteville Formation and Carimona Member (their Spechts Ferry). All three were listed under Hydrozoa, the group that includes relatives of corals and jellyfish, which was a reasonable enough hypothesis at the time (before the discovery of pterobranch affinities, graptolite relationships were a free-for-all):

Winchell, N. H. and E. O. Ulrich. 1897. The lower Silurian deposits of the Upper Mississippi Province: a correlation of the strata with those in the Cincinnati, Tennessee, New York and Canadian provinces, and the stratigraphic and geographic distribution of the fossils. Pages lxxxiii–cxxix in L. Lesquereux, C. Schuchert, A. Woodward, E. Ulrich, B. Thomas, and N. H. Winchell. The geology of Minnesota. Minnesota Geological and Natural History Survey, Final Report 3(2). Johnson, Smith & Harrison, state printers, Minneapolis, Minnesota.

Saturday, September 12, 2015

One more trip to the well... In the spirit of Addendum II, here is my own compilation of undescribed dinosaurs. I am deliberately avoiding repeating entries from the 1982 list (sorry, "Thotobolosaurus", Archbishop, Cleveland-Lloyd ankylosaur, and Monoclonius recurvicornis). In the spirit of that list, I full expect some of these to be named next week and some to be still hanging around, say, thirty-three years from now, like some from 1982 are still waiting in 2015. This is not an exhaustive list, but more of a "greatest hits". It is biased to reports with some history behind them, and also biased to reports that I think will eventually be substantiated, so there's none of the "[random place] [random dinosaur represented by a single bone]". Let me know if they ever get around to "Ngexisaurus".

Saturday, September 5, 2015

We now reach the final section, the part dealing with ornithischians (links to theropods and sauropodomorphs). The ornithischian portion of Glut (1982)'s Addendum II is a real mixed bag. It's not just because people seem to forget about ornithischians, especially when the ornithischians come without bearing horns or plates. There's some really scrappy stuff listed and some really vague entries, as well as two genera that had been named and had entries in the rest of the book, and a third that had been named but hadn't made the book.

Saturday, August 29, 2015

And now we return to 1982. We have seen the future of theropods, now let us turn to the future of sauropodomorphs. One future was that of Supersaurus and Ultrasaurus, a future of every large sauropod having to out-superlative the sauropod before it. This future petered out before it got any farther, kneecapped by an honest mistake half a world away and a terminal case of bonebed chimerism. Another future was that of Roccosaurus, the fanged prosauropod, and it was a terrible bleak cheesy early-'80s dystopian future, with leather and chains and synthesizers. That future never came to pass. Others involved overlooked fossils from Portugal and central Asia taking their rightful places, or promises of skulls from India, or an unusual elongate cervical vertebra from Wyoming, or a skeleton from Tendaguru.

Sunday, August 23, 2015

One of the great mantras of paleontology is "wait for the paper" (occasionally with choice adjectives between "the" and "paper"). Paleontology is, after all, a science of delayed gratification. First you have to find the fossils, then prepare them, then write and submit a manuscript, and then see it published. This process is measured in years in the best of times, and often some information gets out, either intentionally (talks, posters, news releases) or unintentionally (unredacted information in other publications, gossip, etc.). We went over part of this ground before. Here's a group of concrete examples.

Sunday, August 9, 2015

If you thought that echinoderms have a variety of seemingly unrelated body plans today (sea stars, crinoids, sea urchins, sea cucumbers...), you should have seen them during the Paleozoic, when several now-extinct classes populated the oceans. The group with probably the most recognition are the blastoids, or sea buds, which had stalks like crinoids but with a nut-like structure instead of a cup-like structure as the business end. The rocks of the Twin Cities area are not known to have produced blastoids, but they have produced rare examples of four other groups not including the crinoids we saw before. They are: asteroids (sea stars), rhombiferan cystoids, edrioasteroids, and stylophorans (a.k.a. carpoids, a.k.a. homalozoans). Three of these groups are extinct, and it doesn't take much to guess which. This diversity of echinoderms is not particularly unusual; Cincinnatian rocks have all the same classes as well as brittle stars and cyclocystoids (extinct and known mostly from their ring-like outer structures), and the Bromide Formation of Oklahoma, of comparable age, outdoes the Minnesota rocks handily. But for the luck of the cosmic draw, any of these extinct groups might be around today.

Sunday, August 2, 2015

This is part of Devil's Parlor in the Minnesota side of Interstate Park, on the St. Croix River. I was at the park on Saturday for a park geology program, and following work I wandered through the Glacial Gardens section. Interstate Park, as its name suggests, has units in two states, in this case Minnesota and Wisconsin. The two parts are state parks, associated with but not part of St. Croix National Scenic Riverway (the Wisconsin side is also the western trailhead for the Ice Age National Scenic Trail, as well as one of the nine parts of the Ice Age National Scientific Reserve). Interstate Park is known for its glacial landforms, imprinted primarily on Precambrian bedrock.

Sunday, July 26, 2015

For the fossil enthusiast in Minnesota, there are few groups with a bigger gap between "what they show in the books" and "what you actually find" than crinoids. The ideal of a crinoid fossil is a long segmented stem or stalk connected to a cup-like structure crowned by a group of delicate feathery arms. The Digital Atlas of Ordovician Life and the UGA Stratigraphy Lab's pages on Cincinnatian fossils have many images of these ideal crinoid fossils, if you're feeling like living vicariously. The reality in Minnesota is a bit more like this:

Saturday, July 4, 2015

One of the most diverse fossil groups in the Paleozoic rocks of Minnesota is also one of the least familiar to the layperson. This group is the Ostracoda, or "seed shrimp", a class of crustaceans that is still thriving. They owe their lack of familiarity to their diminutive size; they aren't called seed shrimp for nothing. Although found practically anywhere you can rub a couple of water molecules together, they are often more or less invisible to humans because most of them are on the order of 1 mm long. They owe their abundance in the fossil record to their durable shells, being equipped with a pair of valves not unlike a clam. Inside the valves is the tiny crustacean itself, with several pairs of appendages and distinct internal organs. With around 8,000 living species, there's a lot of diversity to go around. Ostracodes (also spelled ostracods) inhabit marine, freshwater, and moist terrestrial settings, are free-swimming or bottom dwellers, and include predators, herbivores, and detritivores. Definite ostracodes appeared during the Ordovician; there are some suspiciously ostracode-like creatures in the Cambrian, such as bradoriids, but they are not currently considered ostracodes. Fossil ostracodes are of particular interest for paleoenvironmental studies (depth, temperature, salinity, etc.) and biostratigraphy. There is one slight drawback to appreciating them as fossils, though: their size. Without a good microscope and the equipment to extract ostracodes, their charms will necessarily be vicarious for most people. Nothing against microfossils (I personally have a fondness for forams, because one of my first projects involved them), but those are just the practical breaks. There is, however, one exception in the rocks of the Twin Cities, a giant among ostracodes, the form commonly known as Eoleperditia fabulites or Leperditia fabulites. This species tops out around a centimeter long and resembles a bean. It can be both common and recognizable in the Platteville Formation.

This is the fabled giant ostracode Eoleperditia (or Leperditia) fabulites, from the University of Minnesota collections.

And here are examples in the wild, in the Platteville Formation (probably Mifflin Member).

Stauffer and Thiel (1941) have their usual list, featuring several dozen species, but it probably won't do much for you unless you have the requisite facilities or are just really good at spotting sesame-seed-sized fossils. Also, there are many publications specifically dedicated to the ostracodes of the Platteville and Decorah, and they're going to be more useful than an uncited faunal list. If you want the true Minnesota Ordovician ostracode experience, a selection of citations includes Ulrich (1890, 1892, 1897), Kay (1934, 1940), Hansen (1951), Cornell (1956), Swain et al. (1961), Swain (1987), Swain and Cornell (1987), and Johnson et al. (1991).

Sunday, June 28, 2015

Here's a couple of quick entries on paleontological research going on in the National Parks. In this case, both examples are Quaternary. It's another case of serendipity: I was looking for the first article, and found the second article in the same volume. Neither Channel Islands National Park or Mammoth Cave National Park are slouches paleontologically, but they do get overshadowed. Places like Big Bend National Park, John Day Fossil Beds National Park, and Petrified Forest National Park get a paper or two every year, so it's nice to shine a light on some of the others.

Sunday, June 21, 2015

To start it off, this being Father's Day as I write, I shamelessly link to my father's Flickr photostream. He's got photos of landscapes and landmarks of places in Hawaii, Arizona, Utah, Washington D.C., South Dakota, Virginia, Idaho, Alaska, and Minnesota. I recommend the eagles on Grey Cloud Island.

Where were we? Yes, the majestic trilobite, the three-lobed former denizen of the deep, the oval with antennae, bearer of the first compound eye, shameless vandal of pristine Paleozoic sediment. Trilobites are one of the most famous types of extinct organism, perhaps not on par with certain vertebrates, but certainly the most renowned fossil invertebrates. (In second place, with plenty of daylight intervening, are ammonites. In last place, maybe edrioblastoids? Some kind of echinoderm, probably.) You can find online information on practically any aspect of trilobites you may want to know about, often lovingly illustrated with photos. You'll probably end up at Trilobite.info sooner rather than later. The American Museum of Natural History also has a good guide, with photos of several of the species mentioned below. Wikipedia and the Kansas Geological Survey have detailed entries, and more photo guides particularly relevant to our slice of time can be found at the Atlas of Ordovician Life, theDry Dredgers, fossilid.info, and University of Georgia pages on the Cincinnatian and Nashville.

Saturday, June 6, 2015

Serendipity is an unsung force in the universe. I was reminded of the power of random connections when I first saw the skull of Regaliceratops peterhewsi. There, parked slightly behind the eyes, were a pair of small but distinct horn cores. It couldn't have come at a more propitious moment (and I'm not saying that just to work in the word "propitious"), because for various reasons I'd recently been kicking around the idea of posting on another ceratopsid with small but distinct brow horns: "Monoclonius" recurvicornis, one of life's persistent mysteries.

Sunday, May 31, 2015

Every so often, you may stumble across a crocodile-like thing lurking at the edge of your typical "two-page spread of all kinds of prehistoric critters" found in popular dinosaur books. If the book is of any quality, it includes a legend identifying the denizens, and the crocodile-like thing will be tagged "Champsosaurus" (if there isn't an error in the legend, of course). Unless you're intrigued by the name, or something else tickles your fancy, you'll probably continue along. There are a lot of crocodiles and crocodile-like things to keep track of, after all. What makes this one unusual?

Sunday, May 24, 2015

I am posting this on May 24, 2015, which also happens to be Bob Dylan's 74th birthday. I considered titling this "A Hard Shell's A-Gonna Crawl", but even I have standards. "Shell" doesn't sound a bit like "rain".

Sunday, May 17, 2015

It is common for fossils in the wild to be found in beds of uncountable fragments, some identifiable to species, others only barely recognizable as fossils. These assemblages are often called "fossil hash", for obvious reasons. Although you can have conceivably make a hash out of just about any kind of body fossil and some kinds of more discrete trace fossils (it takes a bit of creativity here), the term is usually applied to invertebrate fossils. This leads to the phenomenon of "hash slabs" or "hash plates", a more portable portion of a bed of fossil hash. Hash slabs can make great display or educational pieces, and a good slab rewards continued study; you can never find everything the first time, and as you learn more, you are able to find more. [2017/05/08: why have I been using "hash slab" as opposed to "hash plate"? I don't know, except I seem to be the kind of person who just has to reinvent the wheel.]

Saturday, May 2, 2015

Well, sic transit gloria mundi to Chilesaurus, I guess. A couple of days on top of the world, and then hustled off the stage for a tiny-maniraptoran-slash-Batman-cosplayer. Could be worse; at least it's Batman. 'Round here, though, I've never really had much interest in the origins of flight, early bird evolution, or so on, so nuts to Yi. Let's bring Chilesaurus back on the stage for a few more minutes.

Saturday, April 18, 2015

By now, the paleontological world has weighed in on the news that Brontosaurus may in fact be a valid genus after all (Tschopp et al. 2015). If you've got some time (befitting its subject matter, it's not what you'd call a short document), the publication is well worth reading. Alternately, if you are strapped for time or just break out in hives when confronted with anatomical terminology, there are many shorterandlesstechnicalexplorations of the topic. The concise description is that Tschopp et al. ran a number of diplodocid and putative diplodocid specimens through a phylogenetic analysis and then attempted to apply more objective measures than the classic eye test to determine which species should be in which genera. Among the results was the absorption of Dinheirosaurus by Supersaurus, which would make the latter the newest member of the exclusive Morrison–Lourinhã club; the designation of the new genus Galeamopus for longtime problem "Diplodocus" hayi; and the headline finding, that Brontosaurus was distinct from Apatosaurus.

Sunday, April 5, 2015

The cephalopods include a wide variety of tentacled friends. Today, they are represented by a few species of Nautilus and Allonautilus, and an array of squids, octopuses, and cuttlefish grouped under the subclass Coleoidea. Aside from the nautiloids, with their chambered shells, the modern cephalopods are not great for making fossils. The external shell fell out of cephalopod fashion coincidentally not long after the Cretaceous–Paleocene extinction event eliminated almost all of the practitioners, and although there is a history of internal shells in coleoids, those have been reduced or lost altogether by the smart modern coleoid. They still have more resistant beaks, feeding organs (the radula), and tentacle hooks, with some preservation potential, but otherwise you're looking at a lot of soft tissue. What this means is that most of the groups of cephalopods we see today have wimpy fossil records. On the other hand, we know of a great diversity of extinct shelled cephalopods, from three major lineages. The most famous are the ammonites, best known for coiled forms. They appeared by the middle Paleozoic and left the scene at the end of the Cretaceous. Going extinct at the same time, but apparently only extending back to the Triassic, are the belemnites, a subgroup of the coleoids represented by their bullet-shaped internal shells. Finally, there are abundant extinct forms, primarily from the Paleozoic, lumped together as "nautiloids". These early nautiloids had the run of things from the Ordovician to the Devonian, following which they declined until the lineage that includes modern nautilids was the last branch remaining unpruned at the end of the Mesozoic.

Saturday, March 28, 2015

The clam. The oyster. The scallop. The mussel. These are not just names suitable for a low-rank themed superhero or supervillain, but they are also common terms used for some of the abundant and diverse members of the class Bivalvia (also known as Pelecypoda in some references, and Lamellibranchiata if you go back far enough or have a desire to be "that person"). We've already seen the difference between the functional and technical usage of the term "bivalve" with brachiopods, now we get the bivalves that "are" bivalves.

Saturday, March 21, 2015

After about 15 and a half years, I'm no longer going to be maintaining Thescelosaurus.com, expiration date April 9, 2015. It was just one of those things, with a number of reasons behind it. The main one is that I didn't know why I was doing it any more. I'd long ago stopped doing it out of enjoyment and had been doing it out of a sense of obligation. The field of dinosaur paleontology had passed me by years ago,
beginning after my graduation from the University of Colorado at
Boulder, so I was doing it for enjoyment, and if I wasn't enjoying it,
what was the point? The quality of the content was never that hot (I'm not going to claim it was great at the beginning and then declined, because a lot of the initial stuff was pretty hare-brained). As the years went on, the seams resulting from cobbling on this and that were showing, the actual "physical plant" (or whatever the equivalent is for a website) was beyond archaic, and I didn't have the time or, in the end, the desire to bring it up to code. Finally, every year it got a little more expensive, and given the small readership, it occurred to me that I could hear myself talk at cheaper rates.

You'll still be able to find archived versions at Internet Archive, using http://www.thescelosaurus.com/, or if you're really desperate, I'm still going to be holding on to the files. Maybe I'll add to them; I don't know. As for alternative sources, I recommend the dinosaur articles at Wikipedia, which at the very least are on par with my own entries and usually much better (and include sources of information), and the Supplementary Information for Thomas R. Holtz, Jr.'s encyclopedia. In particular, the updated versions of the genera list are like mine, only much better. You're welcome to copy the pages for your own use, but I don't want someone else to continue the website because of my concerns with the quality of the content.

I'd like to thank everyone who made a correction, offered a tip, said hello, or found the site to be useful over the years. I'm glad to have had a good long run. I'll still be writing here, so I suppose I'll have to write a bit more often about dinosaurs to make up for it.

Saturday, February 21, 2015

I generally avoid writing "nuts and bolts" posts about dinosaurs, because there's a lot of people already doing that who know what they're doing. There is, however, one topic on which I'm uniquely qualified to pontificate. In a previous lifetime I was a fresh-faced graduate student who wrote his thesis on possible gut contents in the "Leonardo" specimen of Brachylophosaurus. As such, I spent a fair amount of time considering the history of possible gut contents in herbivorous dinosaurs, which consists of an exclusive club populated by four hadrosaurs, one ankylosaur, and one sauropod. In retrospect, the Leonardo project was somewhat beyond my powers, but I battled on against overwhelming oddities and came out of it eventually. (For you folks playing along at home, by "herbivorous dinosaurs" I mean more or less classic dinosaurs that aren't theropods. I've got nothing against birds, which include many a herbivorous dinosaur, but they aren't why I got interested in these things, and I don't feel sentimental about them being dinosaurs, because "my" dinosaurs are almost all ornithischians and have all been dead for 66 million years.)

Sunday, February 8, 2015

I've been a bit busy lately, so no full post, but here are some historical geologic images and maps of the Twin Cities, 1877–1941. Enjoy!

A map of the surficial geology of Minneapolis and western St. Paul, from Winchell (1877). Note "Finn's Glen" at the end of Summit Avenue, today's Shadow Falls. Also note Bassett's Creek in Minneapolis, once a major waterway but now built over. Some now-defunct quarries and waterfalls are also marked. As far as I know, this and the other maps included here are the oldest published geologic maps for their respective areas.

Small quarries of Platteville stone once dotted the Twin Cities. This is a fairly late example, pictured in Sardeson (1916). Kansan till refers to a now-obsolete system of glacial episodes

Sunday, February 1, 2015

One of the aspects of Paleozoic fossils you learn to appreciate is just how many groups had a brief moment in the sun and then disappeared. I'm not just talking about famous things, like trilobites or ammonites (which saved their best for the Mesozoic, of course). You couldn't wade around in an Ordovician sea without crushing or disturbing something that has no living relatives. In fact, given the diminutive size of most of these things, you would probably endanger an entire fauna with each step, so by all means be careful next time you happen to swing by the Ordovician. Today's spotlight shines on two groups that hang around the fringes of Mollusca, and which show up in small numbers in the Ordovician of the Twin Cities: the hyoliths and scenellids.

Sunday, January 25, 2015

And now we come to the last part, and the reason I started this in the first place: National Park Service Cenozoic nonmarine sedimentary rocks and deposits. I had advance knowledge that the theme for this year's National Fossil Day features would be the Cenozoic, so I thought I'd tag along.

Sunday, January 18, 2015

Quite a number of NPS units record some form of Cenozoic igneous activity, from the obvious (active volcanoes) to the subtle (rock formations that are composed of volcanic debris, or ancient lake deposits that were laid down after a lava flow blocked a river). Restricting the category to just those with Cenozoic igneous rocks still nets quite a few. I decided to go with just those where the igneous rocks are responsible for a headline attraction, or make up a significant part of the bedrock. I've got both a map and a spreadsheet of igneous activity in geologic time, and as you go through you may notice a few patterns. First, a lot of the featured parks have fairly recent activity, roughly Miocene to the present, a span of about 23 million years. Part of this is a natural bias of erosion (younger, less-eroded igneous features are more impressive than old, worn-down features), and part of this is due to the timing of the eruptions themselves. Volcanism on the Rio Grande Rift of New Mexico began shortly before 23 Ma, Great Basin volcanism began around the same time, the Yellowstone Hotspot trail has only been traced back around 16 million years, and the volcanoes of the Hawaii parks only poked out from the ocean during the Pleistocene. Another feature is location. There is a nice arc through southern Alaska, and clusters in northern California–southern Oregon, around the Great Basin–Mojave Desert, in New Mexico, and eastern Idaho–northwestern Wyoming, which correspond to centers of igneous activity.

Sunday, January 11, 2015

I thought it might be interesting to briefly highlight some National Park Service units in terms of geology, and started working in the Cenozoic Era (66 million years ago to the present; you can get a fresh new geologic time scale here). The draft became quite long, so I chopped out the igneous and terrestrial sedimentary parts for later and collected the smaller headings. Many of the following parks have been detailed in NPS Geologic Resource Division publications and maps, which can be found here.

Sunday, January 4, 2015

Winter in the U.S. is not the best time for looking for fossils. It's cold, the days are short, and a significant portion of the ground is covered with snow and ice. There are, however, other places to see fossils than in the field, some of which you may pass every day. Many buildings include fossil-bearing stone, representing sites around the world.